January 2, 2008—White dwarfs are commonly believed to be stellar corpses, the dense, slowly cooling remnants of low to medium mass stars.

So scientists were surprised to find a high-energy x-ray pulse coming from the white dwarf known as AE Aquarii, pictured here in an artist's rendering.

Scientists say the emission looks like that of a pulsar—a rotating neutron star formed after a supernova, the life-ending explosion of a massive star.

"This is the first time such pulsar-like behavior has ever been observed in a white dwarf," said Koji Mukai of NASA, who co-authored a recent paper about the find.

Lead author Yukikatsu Terada, of Japan's Institute of Physical and Chemical Research, added that the discovery means that white dwarfs could be "quiet but numerous" sources of the mysterious cosmic rays that zip through the galaxy.